(1) Field of the Invention
Disclosed herein are an apparatus and method for accurate infrared and visible spectrum scanning of an underlying terrain, detecting defects and integrating high speed acquisition and data processing of roadway and bridge subsurface and surface defects at normal highway speeds.
(2) Description of Related Art
Substantial effort, human resources, and funds are expended on a world-wide basis related to the natural and constant deterioration of roadways, bridge decks, and highway infrastructure. In particular, road surface materials such as asphalt, concrete, and reinforced concrete on bridges, decks and roadways are continuously subjected to degradation due to environmental exposure, wear, and mechanical damage caused by vehicle traffic. Constant degradation of surface materials is further enhanced by regional circumstances including and not limited to normal seasonal climatic cycles, various types of weather, high concentrations of salt-sea air in coastal areas, and exposure to de-icing salts, chlorides and developing types of de-icing chemicals in more temperate regions.
Timely, consistent and comprehensive roadway and bridge infrastructure inspection and assessment is of high importance as it relates to early detection and quantification of various types of deterioration. Without the ability to rapidly and consistently monitor the rates at which roadway and bridge deck surface material is degrading, the likelihood of further accelerated deterioration, without properly applied service and maintenance to avoid such trends, will tend to cause even further accelerated rates of deterioration.
Various methods of infrastructure inspection and assessment have been developed. Known methods range from simple visual inspection to highly complex methods that utilize various tools and electronic devices.
One traditional method involves mechanically dragging heavy steel chain across a roadway or bridge deck surface by hand or tractor. The road surface material is typically concrete in this example. Any changes in the sound that the chain produces as it is dragged along the surface are carefully observed and noted as to the particular locations and areas on the surface itself. Particular changes to the sound produced by the chain may suggest underlying material or structural defects such as, for example, structural cracks or areas of hidden delamination within the concrete. Other mechanical means related to sounding techniques also have been developed and used with varying degrees of success.
The costs and resources required to alleviate and correct rapidly accelerating rates of deterioration tend to increase and accelerate. Further, the effects of roadway and bridge deck deterioration, if left to remain unchecked, will continue to trend toward the compromised safety of motorists and vehicles. Such consequences lead to an even greater sense of urgency to remediate.
The standard civil engineering pavement technique for determining soundness of pavement is chain dragging, hammer sounding, coring and milling of the deteriorated areas. One standard specifying this technique is ASTM D 4580. Many states have their own manual such as MNDOT Concrete Pavement Rehabilitation Manual 5-694.000.
IR scanning of pavement has been evaluated and used for the past 20 years. It is documented in ASTM D4788 (Detecting Delaminations in Bridge Decks using Infrared Thermography).
GPR is documented in ASTM D6087 for evaluating asphalt covered concrete bridge decks using ground penetrating radar. Vertical GPR reflects energy from a difference in material density (reinforcing rod, void, water line, electrical conduit, etc.) which determines the depth.
These techniques collect specific information, but do not solve the unsolved problems summarized above.
Against this background, it would be desirable to identify and locate defects in road and bridge pavements using non-destructive techniques and to characterize those defects in terms of location, area, depth, volume, defect type. Further, if would be useful to be able to collect this information without closing down a road or lane while data are gathered.
Among the references considered before filing this application are: U.S. patent publication documents 2012/0173150; 2012/0218411; 2013/0176424 and U.S. Pat. Nos. 8,803,977; 7,697,727; and 4,910,592.